Fix kw-only marker getting ignored if first in the signature (#340)

Closes: #328

autoapi/mappers/python/objects.py

@@ -13,7 +13,7 @@ def _format_args(args_info, include_annotations=True, ignore_self=None):
     result = []
 
     for i, (prefix, name, annotation, default) in enumerate(args_info):
-        if i == 0 and name == ignore_self:
+        if i == 0 and ignore_self is not None and name == ignore_self:
             continue
         formatted = "{}{}{}{}".format(
             prefix or "",

tests/test_astroid_utils.py

@@ -181,6 +181,13 @@ class TestAstroidUtils:
                     sys.version_info[:2] < (3, 8), reason="Uses Python 3.8+ syntax"
                 ),
             ),
+            pytest.param(
+                "*, a: int, b: int",
+                "*, a: int, b: int",
+                marks=pytest.mark.skipif(
+                    sys.version_info[:2] < (3, 8), reason="Uses Python 3.8+ syntax"
+                ),
+            ),
             ("a: int, *args, b: str, **kwargs", "a: int, *args, b: str, **kwargs"),
             ("a: 'A'", "a: A"),
         ],